Your machine can light up the possibility of bad south bridge is unlikely, the most likely just related to capacitance inductance or insurance damage caused by the send repair it, indeed, only about 30 ~ 40 yuan, of course, you that such as the repair store is not too much if the wool will be more off a little! Even if the I/O is damaged it costs a few bucks, $40 is the limit for conscientious people!
Buying a USB one is fine, but if there's a problem with the real I/O or the southbridge, the USB port may not work (try using a USB flash drive first)! And you have to take up two USB ports, which I personally don't recommend!
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What I mean is that the "USB port" is generally not bad, it's just an interface, the bad is mostly mechanical damage caused by someone trying to plug it in the opposite way (e.g., the USB port is cracked), and we generally say that the USB port is burned, but actually the chip or related circuit components that control it are burned. The chip or related circuit components burned, resulting in the USB port can not, repair is to replace these bad components USB port will be able to use.
You can power on the South Bridge or I/O should be good, just burned off the USB port near the small capacitor inductance, which is good to repair, generally 30 ~ 40 yuan to repair. In this case you can buy another USB keyboard and mouse.
But also does not rule out just burn the South Bridge chip in part of the circuit, the other normal can also boot work, this situation is rare. This is a very rare case. In this case, you can buy a USB keyboard and mouse, and you may not be able to use it. (Computer a lot of things can not be absolute, oh I can not say dead smash their own feet!)
intel is the I/O control USB port, VIA and so on is the south bridge control USB port.